It's all about the money, money, money ... thing is you buy the console cheap, as the true price of the hardware is twice as you pay for it, then you buy games and the original investment - the console - , on your 3rd or 4th AAA game purchase - everyone in the industry it's making money, consoles industry, games developers, distributors, so on ...
As per Exclusive content, there it's not so much of a difference, AAA games will be available on both, sure there will be Uncharted \ Forza \ God of War \ Halo games - but without the competition, prices will go up, quality down and nobody will get what they want.
That's exactly it! It's pretty ridiculous that, for some triple-A titles, a new one I can immediately think of would be Days Gone, is developed with an engine like UE4, which means its very easy to port across all platforms, is stuck on a single platform for no reason other than money... Its a very sad and frustrating time for gamers.